1. Field of the Invention
This invention relates to sheet feeding machines and more particularly to separating a sheet from the bottom of a stack one at a time with the assistance of a vacuum applied through a conveyor belt.
2. Description of the Related Art
Friction sheet feeders are known in the art and are commonly used in printers, plain paper copiers and the like to feed individual sheets, one at a time, from a stack of such sheets into the printer or copy machine. Friction feeders have also been used in mass mailing applications for assembling and collating packages of sheet materials between flights of a conveyor leading to a high-speed wrapper.
It is important in such applications that the friction feeder deliver products one at a time in synchronized relation to the operation of associated equipment accurately, reliably and repeatably. For example, in the mass mailing application, a plurality of friction feeders are arranged along a length of a transversely extending conveyor and each such friction feeder must deliver only one article at the time from its stack onto the conveyor as each defined flight thereof passes the discharge end of the friction feeder. The friction feeder must therefore operate reliably, at high speeds, over prolonged periods and with a minimum operator intervention for clearing jams or multiple feeds.
Relying on friction alone to provide the force necessary to pull a single sheet article by applying force of a belt and wheel is pressure sensitive. Too much pressure will leave scuff marks or otherwise damage the sheet article to be moved. Too little pressure results in the sheet article slipping relative to the wheel or belt resulting in jams or other problems. If glossy sheets of paper or other slippery surfaces on the sheet articles are used frictional contact may be reduced resulting in increased paper jams and a reduction in efficiency of the friction feeder. Further friction contact by wheels or belts may be compromised by chaff of other debris on the sheet articles to be moved reducing the effective friction contact. Adjusting the friction contact pressure of wheel or belts to the proper pressure can be difficult and needs to be set frequently to assure proper operation.
Some sheet feeding machines use air pressure or a vacuum to assist in gripping the sheet article to be transferred. For example U.S. Pat. No. 5,888,047 titled Separating and Feeding Machine for Bound Booklets, issued Mar. 30, 1999 uses a vacuum applied to a reciprocating box under the sheet article to be advanced to apply a force to the article.
The reciprocating box has several drawbacks in that it is constantly on even when the article is being pulled from the vacuum by rollers while the reciprocating box is moving counter to the effect of the rollers.
The device presented improves the performance of a sheet feeder by using a conveyor belt having apertures for use with a vacuum acting through the apertures on the conveyor belt to hold the sheet article on the conveyor belt while moving the article forward. The vacuum supplements the friction of the belt itself and releases the article from suction gradually as each piece moves off of the end of the conveyor belt. There is no reciprocating movement to impede the progress of the sheet article. Further the vacuum helps clean the sheet article and the belt for a better frictional grip by removing chaff and other particles. The vacuum is particularly useful on glossy paper or other slippery surfaced sheet articles to help grip and move the article.
It is an object of the invention to increase the force applied to a sheet article in a sheet feeder machine to separate the bottom most sheet article in a stack of sheet articles from the stack using a conveyor belt.
It is an object of the invention to reduce adjustments needed to apply the correct force to a sheet article to remove it from a stack by frictional contact.
It is an object of the invention to clean the sheet article and the conveyor belt while in use for better frictional contact between the sheet article and the conveyor belt.
It is an object of the invention to reduce jamming and improve the performance of sheet feeder machines.
Other objects, advantages and novel features of the present invention will become apparent from the following detailed description of the invention when considered in conjunction with the accompanying drawing.